Transmission-equalization arrangement



G, K, THOMPSON. TRANSMISSION EQUALIZATION ARRANGEMENT.

APPLICATION FILED OCT, 2. I9I9.

WNJU V, Wa

5 ggd/i IOJIIISIIQQJIJ lGLElOItMEtE K. THOMPSON", OF MAFLEWOOD,

NEVI JERSEY, ASSIG- NOR TO AMERCAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF ANEVI' YORK.

TRANSMISSQION-EQUALIZATION ARRANGEMENT.

incassi..

Specification of Letters Patent.

Patent-eu een. s, 192i.

appiicanon inea october e, i919. semi no. eef/,eea

of means whereby the electrical characteristics of telephone lines may be equalized or rendered more uniform.

rlelephone lines have, general, different electrical characteristics varying with .the lengths of the lines. For any particular type-of line construction which may be einployed the resistance, capacity, inductance and leakage of the circuit increase with the length. rlhese variations in the electrical characteristics of the dierent subscribers linesin a telephone system introduce a number of variable effects inlthe telephone service rendered fromdifferent stations.' `For example the different electrical characteristics result'in different degrees of attenuation in the alternating telephone current passing over-the subscribers lines and thus give louder and more effective telephonie communication to subscribers connected by means of shoit lines than to subscribers connected by means of long lines. itsv a result, a subscriber having a long line, when connectedv with any other subscriber, does not receive as good telephone transmission as would a subscriberl having a short line similarly connected. Furthermore, in thd common battery systems now so generally emA ployed in all but Vsmall communities, the resistance of theline causes a further effect on thev transmission in that it reduces the amount of direct current which the transmitter receives from the central office battery and so renders it less efficient in the generation of the alternating telephone current. Likewise in common battery systems employing electro-magnetic receivers this variation in current supply introduces 4changes in the efficiency of the receiver which are undesirable.

ln view of the conditions above referred to, it has not been heretofore possible to provide all subscribers with the same grade of transmission and it is one of the objects of this invention to provide means whereby Vhis difficulty may be overcome and transf mission over different lines'equalized. Other and further features of the invention willA appear from the description hereinafter given.

ln the arrangements of this invention the transmission equalizing means, which are operated by a solenoid type relay, are associated with connecting circuits by which connections are established 'with the subscribers lines rather than with the lines themselves, as in former arrangements. In one of the arrangements of the invention a solenoid relay, which is included in the cur-y rent supply circuit of the connecting circuit operates to pull apart the windings of coiled spring resistances in each side of the line of the talking circuit whenever the current flow mission over subscribers lines of differing .electrical characteristics.

. In another arrangement of the invention the coiled spring yresistances may be replaced by graphiteresistance rods controlled by the solenoid relay and which move along line contacts in the circuit and cause. the resistance in series with the line to change as the solenoid `relay opcrates. In l another alternative `arrangement the graphite resistance rods are employed but the line contact springs are replaced with granular Acarbon i chambers through which the rods are moved by the solenoid.

The invention may be more fully understood from the following description taken in connection with the accompanying drawings in the Figures l, 2 and 3, of which are illustrated a preferred forml and modifications of the invention. Similar reference numerals have been used to denote like parts in all of the figures of the invention.

' In the arrangements of the invention illustrated in Fig. l the transmission equalkizing device is shown for purposes of conil l' relatively small resistance to the talking the plug F, adapted to cenet Wit oli subscribers luie7 auch li. with the subscribers line lL may be any desirable type oi sub-statioi'i apparatus 2. lncluded in the talking. conductors ci the cord circuit l are the coiled spring resist. ances 7 and d, the windings oi which are normally close together and hence present current. The spring resistancesiv and 8 are connected to a plunger 2U oit a solenoid operated relay 6, the Winding of which is included in the current supply circuit of the cord. lr the plug P is inserted in the jack d 'of av subscribers line, such as L, the

current supply for the connection will be completed over the following circuit; from ground and battery, Winding ot relay 6, conductor 5, upper right hand winding of transformer 3, tip conductor of cord l,

spring resistance 7, tip conductor of cord l, tip contacts of plug l? and jack J, tip

-conductor of line L, through the sub-station apparatus 2, over the ring conductor of line l, ring contacts of jack l and plug P, over the ring conductor of cord l, spring resistance 8 ring conductor ci: cord l, lower right hand Winding of transformer 3, over conductor 4r, to ground; lf the resistance of the line L, with which a connection is made, is smaller than that of a line adopted as a standard, the current How over the above traced circuit will primarily be greater than desired and, accordingly, will operate the solenoid relay 6. This will cause plunger 20 to `be drawn into the core or" the relay and will cause the windings ol' the spring resistances 7 and 8 attached thereto to be separated. lAs the windings separate, the resistance of the spring resistances 'Z and8 is increased, thereby increasing the resistances in the circuit and decreasing the current flow thereover. As the relayv 6 is adjusted to operate only with currents of and above a predetermined desirable value, the relay 6 Will continue to operate and increase the resistance of the spring resistances,` 7 and 8 until the current iow over the circuit has been reduced to the'aforeinentioned predetermined desirable value, at which time relay 6 will stop its operation. As the current flow over the talking circuit vis determined primarily by the resistance of the subscribers line With which a connection is made, the device of the invention affords a means for automatically regulating the current flow to a predetermined and desir able value over lines of differing electrical characteristics,l thereby equalizing transmission over such lines.

In Fig. 2 the coil spring resistance elements 7' and 8 are replaced by graphite resistance rods 9 and l0, which are attached to the plunger 20 of the solenoid relay 6 and which move along the line contacts 11 specific the solenoid replaced with granular carbon-chambers 13 and la, through which the rods are moved by the solenoid relay. ris. the operation o'f .the arrangements illustrated in 'ltigs and 3 is substantially the same as the operation of the device of lig. l, no further description thereof' Will be given.

lil/'hilo the arrangements and transmission equalizing devices of the invention have been illustrated for purposes of convenience as associated with cord circuits, it is pointed out that they may equally Well be associated with other. forms of connecting'circuits, Such as trunk lines, and also may be used in connecting means employed in automatic telephony, such as in district or incoming selectors in such systems. -Accordingly, while the arrangements for the invention have been disclosed as embodied in certain arrangements which have been deemed desirable, it is understood, thatthey are capable of embodiment in many and Widely varied forms Without departing from the spiritof the invention as define in the appended claims. i

What is claimed is:

l. In a telephone system, a plurality of subscribers lines of diii'ering electrical characteristics, a connecting circuit for establishing connections with' said lines, a lvariable resistance included 4in the talking y circuit of said connecting circuit, and a sole- 105 noid operated relay included in the current supply circuit of said talking circuit for varying said resistance in inverse proportion to the resistance of the line With which a connection is established.

2. In a telephone system, a plurality of subscribers7 lines of differing electrical characteristics, a connecting circuit for establishing connections with said lines, a vari able resistance included in the talking circuit of said connecting circuit, and a solenoid operated relay included in the current supply circuit of said talking circuit and adjusted to operate only with currents of and above a predetermined desirable value for 120 varying said resistance in inverse proportion to the resistance. of the line with which a connection is established.

3. In a telephone system, a plurality of subscribers llines of differing electrical characteristics, a connecting circuit for establishing connections with said lines, a talking circuit included in said connecting circuit, convolutions of resistance Wire normally closed included in series in said talking cir Lemmi' solenoid relay for extending said convolu-` tions of resistance Wire thereby increasing.

y the resistance of said talking circuit.

4. In a telephone 'system5 a plurality of subscribers lines of diering'eleetrical characteristies, a connectine" circuit for establishing connections Witlv said lines7 la sole! noid operated relayincluded inthe current supply circuit of said 'connecting eircuit, the operation 'of said relay'beingV controlled by theV electrical characteristics of seribers line With which a yconnection is made,

a yariableresi'stance included in series in said talkingc'lrcult, and means controlled the sub# by vsaid solenoid i'elayoi increasingsaid f *variable resistance.

' aina'telephone'system,fa plurality oi subscribers lines of differing electrical chan acteristics, va connecting circuit for establishing connections With said lines, and means in said connecting; Circuit for rendering the transmission over said lines .uniform said last mentioned means bein controlled by a solenoid operated relay -inc uded in the current supply circuit ofsaidk connecting means, said relay being controlled by the resistance of the line vwith which a connection is established.

ln testimony whereof, I; have signed my name to this specification thisBOth day 025i SeptemberLlQlQ.. .L s

GEORGE K. THoMieson 

